Elephant trunks

sugatam · 06 June 2012, 15:44

My RIB is docked at a marina - it is fitted with two transom scuppers with elephant trunks. The scuppers are a few inches above the waterline. I'm curious what people do in this situation - leave the trunks down, or raise them? I'm worried if I leave them down, some seawater will get in if it gets a bit windy, and of course, I'm worried about rainwater in the other case. Should I leave them down, but also install a one-way valve for protection? Suggestions welcome!

jyasaki · 06 June 2012, 16:17

Up. They won't drain much if the boat's not moving anyway.

jky

captnjack · 06 June 2012, 16:18

Quote:

Originally Posted by sugatam

My RIB is docked at a marina - it is fitted with two transom scuppers with elephant trunks. The scuppers are a few inches above the waterline. I'm curious what people do in this situation - leave the trunks down, or raise them? I'm worried if I leave them down, some seawater will get in if it gets a bit windy, and of course, I'm worried about rainwater in the other case. Should I leave them down, but also install a one-way valve for protection? Suggestions welcome!

Since they are above the waterline any water sloshing up against/into them when they are down will just drain away. So I'd leave them down. If they were below the waterline I might think differently.

willk · 06 June 2012, 21:28

If they're above the waterline at rest, why bother with elephant's trunks?

Surely you could just leave them open like these?

Portnahaven · 06 June 2012, 22:48

My draining arrangement is same as Willks photo. I had about 3 inches drop from the floor to the transom. I found even slow reversing, a fair amount of water gushed in. O.K. once in forward it all went out again. But the floor was always wet.
I got the floor raised by two inches and this drop sorted it out.
I would be a bit worried with your drop - tied up in marina, waves pushing from the back could allow in a fair bit of water.

sugatam · 08 June 2012, 01:26

Thanks everyone for the responses. I looked closer - it is worse than I thought - the scuppers barely clear the waterline - by an inch at most. Plus, the shape of the trunks is such that the moment they're let down fully, the bottom part sags and scoops up quite a bit of water. The only way I can deal is if I add some scupper valves in addition to (or instead of) the trunks. Anyone know where I can get valves for a 4" drain tube? All the ones I've seen are considerably smaller.

Ribstore · 08 June 2012, 07:35

Sugatem,

Scuppers, trunks, self-bailers etc are designed to move deck water whilst underway, you will need a bilge pump for shifting water when moored. Trunks are very effective at shifting deck water fast when underway as they have no valve restricting the water flow but are ideal for taking water on-board if left down when moored! It is a case of using the right tools for the right job!

9D280 · 08 June 2012, 09:16

Non return valves will never seal! All you need is the smallest bit of grit in there and you might as well not have them. The best they can do is prevent a mass ingress when you stop.

The other option might be one of these "mooring rope" pumps, although a Rib in a marina might not have enough movement for one to work.

jambo · 08 June 2012, 17:21

The other option might be one of these "mooring rope" pumps, although a Rib in a marina might not have enough movement for one to work.[/QUOTE]

Your're right they dont work as you need more movement. I tried one absolute waste of time for my set up on swing mooring in sheltered bay.

captnjack · 08 June 2012, 18:31

Quote:

Originally Posted by sugatam

Thanks everyone for the responses. I looked closer - it is worse than I thought - the scuppers barely clear the waterline - by an inch at most. Plus, the shape of the trunks is such that the moment they're let down fully, the bottom part sags and scoops up quite a bit of water. The only way I can deal is if I add some scupper valves in addition to (or instead of) the trunks. Anyone know where I can get valves for a 4" drain tube? All the ones I've seen are considerably smaller.

How are the trunks "scooping" water while at rest and above the waterline? (even if just slightly) As long as the deck slopes aft I don't see what the problem is with leaving them down - apart from possible marine growth on the fabric.